t/t5620-backfill failure on s390x

Hi,

I see a new (and consistent) failure in 2.49.0-rc0 for t5620.4 'do partial clone 2, backfill min batch size' on s390x:

expecting success of 5620.4 'do partial clone 2, backfill min batch size':
        git clone --no-checkout --filter=blob:none      \
                --single-branch --branch=main           \
                "file://$(pwd)/srv.bare" backfill2 &&
        GIT_TRACE2_EVENT="$(pwd)/batch-trace" git \
                -C backfill2 backfill --min-batch-size=20 &&
        # Batches were used
        test_trace2_data promisor fetch_count 20 <batch-trace >matches &&
        test_line_count = 2 matches &&
        test_trace2_data promisor fetch_count 8 <batch-trace &&
        # No more missing objects!
        git -C backfill2 rev-list --quiet --objects --missing=print HEAD >revs2 &&
        test_line_count = 0 revs2
+++ pwd
++ git clone --no-checkout --filter=blob:none --single-branch --branch=main 'file:///tmp/git-t.sYdo/trash directory.t5620-backfill/srv.bare' backfill2
Cloning into 'backfill2'...
+++ pwd
++ GIT_TRACE2_EVENT='/tmp/git-t.sYdo/trash directory.t5620-backfill/batch-trace'
++ git -C backfill2 backfill --min-batch-size=20
++ test_trace2_data promisor fetch_count 20
++ grep -e '"category":"promisor","key":"fetch_count","value":"20"'
error: last command exited with $?=1
not ok 4 - do partial clone 2, backfill min batch size

I don't know enough about the backfill command to even guess what's wrong, but hopefully this is helpful to those who are more familiar with it. (Stolee, party of 1? ;)

I don't have shell access to the s390x host, but can run the test suite with additional debugging if needed. I have the test-results directory from the build as well.

Thanks,